Richard W. Orloff, a leader among conservative Republicans in Upper Bucks County, said yesterday he would challenge state Rep. David W. Heckler for the GOP nomination for the vacant state Senate seat.

Orloff said he had been preparing to enter the race since former Sen. James C. Greenwood won the congressional election in November, but he would probably have backed out had either Thomas J. Rosko, the county coroner, or state Rep. Paul I. Clymer remained in the contest.

Rosko and Clymer are both conservatives. Both decided within the past few weeks to drop out of contention for the 10th District Senate seat.

"If Paul ran, it would have changed the dynamics," said Orloff. "I would ultimately have supported Paul."

But now with Rosko and Clymer out of the contest, Orloff said that conservative Republicans need an alternative to Heckler.

The seat became vacant when Greenwood resigned to be sworn in as U.S. representative in the 8th District earlier this month.

The vacancy will be filled through a special election, which has been set for July. There will be no primary for the special election. Next month, the two major political parties are expected to caucus to select their candidates.

Heckler was the first candidate to announce for the seat, but he has met consistent resistance from conservative Republican leaders, who were counting on either Rosko or Clymer to contend for the nomination.

Conservatives believe Heckler is too closely associated with the moderate wing of the party. Heckler, a Doylestown Republican who represents the 143rd District, was an aide to former Sen. Edward L. Howard.

Heckler favors abortion rights and has said he intends to continue Greenwood's work in the Senate for a less-restrictive abortion law in Pennsylvania. Orloff opposes abortion rights.

Orloff said he intends to make direct appeals to the 205 Republican committee members who will vote on the nomination. He conceded that, at this point, Heckler is the front-runner.

"I'd have to say the advantage tilts to Heckler since he is a sitting state representative," said Orloff. "But there are a lot of people unhappy with Dave Heckler."

Orloff, 38, works as an internal auditor and has previously been an unsuccessful candidate for Richland Township supervisor. He is a member of the Bucks County Water and Sewer Authority and is a leader in the Quakertown Area Taxpayers Association.